1. Field of the Invention
The present invention relates to a turbomachine comprising a device for the adjustment of the clearances of a labyrinth seal which provides sealing between a rotor and a stator, the device also facilitating the alignment of the means defining the main gas flow of the engine. The invention also relates to a method for the application of the adjustment of the clearances of the seal.
2. Summary of the Prior Art
Research into high performance current turbomachines requires consideration of different aspects, amongst others, the efficiency and the production of maximum thrust. As a result the engines are always highly sensitive to the thermal conditions and also are particularly sensitive to the boundaries of the operational parameters leading to surging.
With a view to displacing the surging boundaries further from operational ratings and to reduce this sensitivity, particular attention must be applied to secondary phenomena arising during operaton of the machine: losses of fluid-tightness lead to the need for research into a perfect matching of the clearances during operation between the fixed and the rotary parts, recirculations which are always to be avoided, and defects in the alignment of the elements of the walls defining the main gas flow of the engine.
Such problems are encountered in particular at the roots of rotor blades and also, it is these problems which the invention seeks to overcome, between the inner diameter of one stage of the stator and the corresponding rotary part of the rotor, that is to say the region of the labyrinth seal in the zone where problems of non-alignment are also encountered in the main gas flow between the edges of the rotor blades and the stator elements constituting the inner wall of the gas flow defining passage.
As is conventional, the labyrinth seal used comprises two parts: annular lips, teeth or blades carried by a disc of the rotor and also a sealing ring. Such sealing ring is rigid radially with the inner side of the blades constituting one stage of the stator and supports a layer termed "abradable" capable of co-operating with the annular lips and of wearing on contact in order to ensure sealing under all operational conditions without risk of interference contact liable to give rise to damage.
Various devices have been used for adjusting the clearance between the sealing ring and the rotor, in response to the operational conditions of the engine. Thus, for example, U.S. Pat. No. 4,127,357 describes such a ring support device of a turbine in which the radial position of the segments constituting the ring is adjusted by means of a mechanism comprising a shaft support mounted eccentrically and driven in rotation by a toothed ring which is displaced independence upon variations of the operational parameters of the engine. This device applied to a fixed stator ring cannot however, be used for adjustment of the angular configuration in order to vary the angle of incidence of the blades, for example by means of a rotary pivot. The complexity of the device incorporating the use of an eccentric may give rise to disadvantages.
An object of the present invention is to overcome the disadvantages of previous proposals and to enable resolution of the problems referred to hereinbefore.